Police officers guard a cordoned off area in the city centre where former Russian intelligence officer Sergei Skripal and his daughter Yulia were found poisoned, in Salisbury, Britain, April 3, 2018. REUTERS/Hannah McKay

What Is Known, and Not Known, about Poisoning of Ex-Spy in Britain

Former Russian double agent Sergei Skripal remains critically ill in hospital more than a month after he was poisoned with a nerve agent in the southern English city of Salisbury

This is what we know – and don’t know – so far:

WHAT HAPPENED?

At 1615 GMT on March 4, police received a call from a member of the public about two people who were acting strangely. The police found Skripal, 66, and his daughter, Yulia, 33, unconscious on a bench outside The Maltings shopping centre in Salisbury. The pair were taken to Salisbury District Hospital.

A police officer, Detective Sergeant Nick Bailey, was one of the first to respond to the incident. He was taken to hospital and later released.

Britain said more than 130 people were affected by the attack. More than 50, including three children, reported to hospital.

WHAT POISONED THEM?

On March 12, British Prime Minister Theresa May said the couple had been poisoned with a military-grade nerve agent from the Novichok group of poisons developed by the Soviet Union in the 1970s and 80s.

There are several variants of Novichok, a binary weapon containing two less toxic chemicals that when mixed react to produce a poison several times more lethal than sarin or VX.

Russia’s ambassador to Britain, Alexander Yakovenko, has identified the alleged poison as Novichok A-234, derived from an earlier version known as A-232.

May said her government had concluded that it was “highly likely that Russia was responsible” for the poisoning or that it had lost control over some of the nerve agent.

Russia has denied involvement and Russian officials have suggested the British secret services, possibly with U.S. help, poisoned the Skripals to stoke anti-Russian hysteria.

Russian President Vladimir Putin has said it is nonsense to think that Moscow would have poisoned Skripal and his daughter.

“Russia does not have such (nerve) agents,” Putin said on March 18. British Foreign Secretary Boris Johnson said it was overwhelmingly likely that Putin himself made the decision to attack Skripal, an accusation the Kremlin said was shocking.

DIPLOMATIC FALLOUT

May gave Russia a day to provide an explanation but none came. On March 14, she ordered 23 Russians who she said were spies working under diplomatic cover to leave Britain.

On the eve of its March 18 presidential election, Russia ordered 23 British diplomats out of Moscow. It also shut down the activities of the British Council, which fosters cultural links, and Britain’s consulate-general in St Petersburg.

The leaders of the United States, Germany, France and Germany condemned the first known use of a military-grade nerve agent in Europe since World War Two, saying it threatened the security of the West.

In the biggest Western expulsion of Russian diplomats since the height of the Cold War, the United States ordered out 60 Russians and Moscow responded by expelling 60 U.S. diplomats. Other Western countries then expelled about 70 Russians and the Russians largely followed suit.